A worker on the work platform of pier no. 12 watches as a 200 ft crane maneuvers a huge drill bit into a shaft that will guide it to the river bottom below--to the bedrock level to make room for the footings for the new bridge just south of Stillwater on Monday afternoon July 22, 2013. (Pioneer Press: John Doman)

The work platform (at left) fills up the barge (at right) with material that comes up from the St. Croix River bottom, mostly muck and sand as initial work progresses in the putting in of the footings of the new bridge on Monday afternoon July 22, 2013. (Pioneer Press: John Doman)

Some spot welding is done on a casing which will eventually be set into place inthe bedrock of the river bottom to bring up material from the St. Croix River bottom, mostly muck and sand-- as initial work progresses in the putting in of the footings of the new bridge on Monday afternoon July 22, 2013. (Pioneer Press: John Doman)

Out on the St. Croix River, construction of Piers 8, 9 and 12 of the new bridge south of Stillwater is underway.

At Pier 9, on the Minnesota side of the river, crews use a 2 1/2-foot-wide bit to drill through a layer of muck at the bottom of the river and then bring the bit, coated with a gray silt-like material, to the surface. The drill operator swings the bit over a plastic lining to catch water drips and stops when he gets to a spot above an adjacent barge.

Then, like a baker trying to get the last of the cake batter off the beaters of a hand mixer, he spins the bit in the opposite direction. Sand, mud and gravel fall to the half-filled barge below.

Across the river, at Pier 12 near the Wisconsin shoreline, crews are hauling huge buckets of sand from the bottom of the river and loading them into another barge.

By the time the five piers in the river are complete, 25,000 cubic yards of muck, sand and gravel will have been dredged up.

That’s 2,500 dump truck loads. Imagine, if you will, a football field piled high — goal line to goal line — with 14 feet of the stuff.

“At some piers, we have to excavate 10 to 12 feet of muck,” said Jon Chiglo, who is overseeing the bridge project for the Minnesota Department of Transportation. “It’s a very fine, silky material. It doesn’t provide any structural support for us at all.”

Crews must dig through the muck and twist through 30 feet of bedrock before they can anchor the drilled shaft — a deep foundation that is constructed by placing fluid concrete in a drilled hole — to the bedrock.

The road to the bedrock stage of bridge construction hasn’t been easy. After decades of controversy that reached all the way to Congress and President Barack Obama, barges began arriving in April to begin construction of the most expensive highway project in Minnesota’s history.

The new four-lane bridge will replace the aging Stillwater Lift Bridge as the main Minnesota-Wisconsin crossing north of Interstate 94. It will divert thousands of daily commuters out of Stillwater’s historic downtown and route them instead to Minnesota 36, through Oak Park Heights. The lift bridge will be converted into a crossing for bicyclists and pedestrians.

The new bridge will be a little less than a mile long — 5,100 feet — and will have more than 600,000 square feet of deck area, making it Minnesota’s second-largest bridge by deck area and seventh-longest.

The project — estimated to cost $580 million to $676 million — also includes building three miles of four-lane highway on Wisconsin 35 and rebuilding about three miles of Minnesota 36 and 95.

COMPLICATED BY MUCK

One of the reasons the price tag for the bridge is so high is muck. The bottom of the St. Croix River is soft, making the design for the new bridge’s foundation complicated, Chiglo said.

Crews must drill 100 feet to reach the river’s limestone foundation — that’s about 20 feet deeper than was drilled for the new Interstate 35W bridge in the Mississippi River.

Workers are using a drilled-shaft construction method and installing 40 steel circular casings — each 9 feet in diameter. They drill about 25 feet below each casing to anchor the drilled shaft into the bedrock, Chiglo said.

“Once that is done, they clean out the hole like a big vacuum and lower a big rebar cage into that and pour it full of concrete,” he said. “The concrete is more dense than the water, so the water is displaced by the concrete. As you start pouring the concrete in, you pump the water out as you’re filling it up with concrete.”

Crews from Plain, Wis.-based Edward Kraemer & Sons — the company MnDOT hired to fulfill a $36.7 million foundation contract — are trucking the muck to a former rest area owned by the Wisconsin Department of Transportation about a half-mile south of where the bridge will cross. Motorists on Wisconsin 35 could experience delays in the next two weeks to accommodate the increased truck traffic.

Because of confusion over the permit process in Minnesota, some muck was taken to SKB Environmental Inc. in Rosemount, a solid-waste disposal site, about 30 miles away, Chiglo said. Kraemer & Sons is working to get all of the permits in place to begin taking the sand and gravel to other disposal sites in Minnesota, he said.

In the meantime, the materials will be taken to the rest-area site and to a spot on Wisconsin 64 between 150th Avenue and St. Croix County Road V. The sand and gravel could be used to build the approach on the Wisconsin side of the river, said David Solberg, project manager for the Wisconsin Department of Transportation.

“The material is tested regularly, and it is clean,” Solberg said. “There are no signs of contamination.”

The excavations from the bottom of the river are expected to produce about 500 truckloads of muck a month; that’s 125 truckloads a week, on average.

So far, no gold coins or antiquities have surfaced.

“We have not found anything interesting, which is good,” Chiglo said. “We want to be dull. A lot of what we’re finding, especially on Pier 12 on the Wisconsin side of the river, is very good, clean sand.”

Selling the sand for profit wasn’t part of the equation, he said. Disposition of the material was included in Kraemer’s bid for the foundation contract.

THE WORK

The bridge will have two abutments and 13 piers, five of which are in the river; each pier in the river has two support towers that will anchor the bridge’s cable stays. Piers 1-7 support the bridge on the Minnesota side of the river. Pier 8 sits closest to the Minnesota shoreline; Pier 12 is across the river on the Wisconsin side.

The foundations for Piers 8, 9 and 12 will be done by the end of this year. If Kraemer & Sons finishes the foundations for Piers 10 and 11 by mid-January, the company will get a $1.5 million bonus, Chiglo said.

Kraemer’s work includes building 40 shafts, 10 footings — five sets of two, and the “starter segments” of the piers, Chiglo said. The 10 starter segments will stick out about 15 feet above the river and should all be visible by the end of the year, he said.

The next large contract for the project, expected to be worth $280 million to $310 million, will be advertised in August and let in October. It will cover all the remaining work on the bridge — the superstructure, the substructure and all the approach spans, Chiglo said. “They will build both abutments, all the remaining piers and start where the starter segments end and build above that,” he said.

During a boat tour of the construction site Monday, workers floating on the St. Croix River were building a 50-by-50-foot concrete platform, which contained four large holes, near the old barge moorings at Xcel’s Allen S. King power plant in Oak Park Heights.

Eight concrete platforms are being built and floated out to the sites of Piers 9, 10, 11 and 12. There, they will be secured and become the work areas for crews doing the digging, drilling and dredging. The concrete platforms eventually will be submerged and become the bottom form of the footings, Chiglo said.

At Pier 12, a construction worker welded one of the 9-foot casings that will be pounded into the riverbed while other crew members brought up bucket-loads of sand.

One of the piers — Pier 8 on the Minnesota side of the river — requires a different type of construction. Crews will build a 25-foot-deep, steel-sided cofferdam — a temporary, watertight enclosure — that will give crews a dry area to work, Chiglo said.

‘A BRIDGE PEOPLE CAN BE PROUD OF’

When the foundation work is complete, crews will build a casting yard where more than 1,000 concrete segments will be created. The precast segments, 44 feet wide, 18 feet tall and up to 150 tons each, will form the bridge deck.

“They’re not as tall as the ones we had on 35W, but they’re very large segments,” said Chiglo, who also oversaw the I-35W bridge rebuild. “So the logistics of where they are casting them and how they are going to get them to the river are going to be challenging.”

Although some of the segments could be installed at the end of 2014, he said, most of the installation will be done between April and November 2015. “It’s temperature-driven,” Chiglo said. “The grouting of the tendons, which are a standard element of the bridge, requires temperatures to be above freezing.”

The piers are being built in an order that was “driven by the design and the importance of having Piers 8, 9 and 12 up and aging longer than the others,” Chiglo said.

The new bridge will stand more than twice as high as the Lift Bridge and more than three times as high as the Interstate 94 bridge to the south. It will start 110 feet above the river at Oak Park Heights and rise to 140 feet at Wisconsin.

The extradosed design — a hybrid of a concrete box girder structure and a cable-stayed structure — is lower in height than a typical cable-stayed bridge.

The country’s first extradosed bridge is the Pearl Harbor Memorial Bridge at Interstate 95, currently being built in New Haven, Conn.

Extradosed bridges, which have been built in Japan, Europe and Canada for several years, minimize environmental impact because tower heights are below the river bluffs and there are fewer piers in the river, Chiglo said.

The new St. Croix bridge has a long history filled with controversy. After decades of debate and legal challenges, Obama signed legislation in March 2012 exempting it from the Wild and Scenic Rivers Act, which had been blocking the project.

Now that construction is under way, Chiglo said, there are high expectations — locally and nationally.

“I think it’s a bridge that people can be proud of, and I think it’s a bridge that will draw recognition to the St. Croix River Valley from across the nation,” he said.

Mary Divine is a reporter for the St. Paul Pioneer Press. She covers Washington County and the St. Croix River Valley, but has also spent time covering the state Capitol. She has won numerous journalism awards, including the Premack Award and the Minnesota Society of Professional Journalists' Page One Award. Prior to joining the Pioneer Press in 1998, she worked for the Rochester, Minn., Post-Bulletin and at the St. Joseph, Mo., News-Press. Her work has also appeared in a number of magazines, including Mpls/St.Paul Magazine, Twin Cities Business Monthly and Minnesota Magazine. She is a graduate of Carleton College and lives in St. Paul with her husband, Greg Myers, and their three children, Henry, 15, Frances, 13, and Fred, 10.

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